A systematic study of the potential response of platinum electrode to various redox species in ClO2-based chemical oscillators proves that it is the Cl(+4)/Cl(+3) redox pair that determines the potential in these systems. According to the results reported here, the electrode potential can be predicted from known concentrations of the Cl(+4) and Cl(+3) species, or inversely, these concentrations can be estimated from the measured potential. Thus, at constant ClO2 levels the platinum behaves as a "chlorite selective" electrode. To demonstrate the feasibility of this approach, potentiometric oscillations were recorded in two different ClO2-based oscillating systems, and the experimental results were compared with potentiometric traces calculated by two alternative models.